Layer-by-layer nanoparticles for cytokine therapy in cancer treatment

ABSTRACT

Disclosed are particles for delivering cytokinese, such as IL-12, for the treatment of cancer. The particles comprise cytokines non-covalently bound to liposomes, where the liposomes are coated with polyelectrolytes.

RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Pat. Application serial No. 62/578730, filed Oct. 30, 2017, the contents of which are hereby incorporated by reference.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with Government support under Grant No. W81XWH-13-1-0151 awarded by the U.S. Army Medical Research and Material Command. The Government has certain rights in the invention.

BACKGROUND

Effective cancer treatment is a challenge due to the heterogeneity of cancer as a disease. The term “cancer” covers hundreds of malignancies that differ based on mutation history and tissue of origin. These differences can make targeting treatment very difficult.

Immunotherapy uses a patient’s immune system to recognize and fight tumors. Immunotherapies come in a variety of forms, including monoclonal antibodies, cancer vaccines, checkpoint inhibitors, and general immune stimulants. Cytokines (such as IL-12), which are small signaling proteins used by the immune system to control immune responses, can be used as a general immune stimulant when delivered exogenously. This class of treatment refers to a drug that simply activates the immune system in the local environment where it is delivered.

However, cytokine therapies often result in high off-target toxicity. Thus, there is an unmet need for compositions and delivery methods for cytokines to reduce systemic side effects.

SUMMARY OF THE INVENTION

The present disclosure provides a particle for cytokine delivery useful in cancer treatment. Such particles may have properties advantageous in cancer immunotherapy, while reducing systemic side effects.

In some embodiments, the invention relates to a particle comprising a liposome, wherein the liposome comprises a first lipid covalently bonded to an affinity ligand; and the first lipid forms an outer surface of the liposome. In certain embodiments, the invention relates to a particle comprising a protein covalently bonded to a tag, wherein the tag is associated with the affinity ligand. In certain embodiments, the invention relates to a particle comprising a polymer coating, wherein the polymer coating comprises: at least one layer including a polycation, wherein the polycation is non-covalently associated with the outer surface of the liposome; and at least one layer including a polyanion, wherein the polyanion is non-covalently associated with at least one polycation layer.

In certain embodiments, the invention relates to a pharmaceutical formulation comprising a plurality of particles and a pharmaceutically acceptable carrier.

In certain embodiments, the invention relates to a method of treating cancer comprising administering to a subject in need thereof a therapeutically effective amount of a particle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic representation of different loading techniques for a liposomal core nanoparticle loaded with scIL-12.

FIG. 1B is a bar graph showing encapsulation efficiency (left bar, measured as percent of initial IL-12 loaded in final particle) and weight% loading of cytokine (right bar) for different loading techniques in final layered particles. Optimized HEP and Optimized Ni refer to optimization of layering and purification techniques. Ni-HIS associated loading offers the highest encapsulation and wt% loading of cytokine by incorporation through attachment of the cytokine HIS tag to a Ni chelated on lipid head group.

FIG. 2A is a plot showing IFN-γ responses as measured by ELISA to different scIL-12 formulations after incubation with whole isolated splenocytes for 18 hours.

FIG. 2B is a plot showing co-culture activity of scIL-12 formulations in MC38 tumor mimic (Briefly, scIL-12 formulations were incubated with MC38 tumor cells for 6 hrs, cells were washed with PBS, whole splenocytes were added for 18 hrs, IFN-γ levels were measured with ELISA.

FIG. 2C is a bar graph showing the quantification of EC50 calculated from FIG. 2A.

FIG. 2D is a bar graph showing the quantification of EC50 calculated from FIG. 2B. Only treatments that have shown tumor cell association in the past (HA, PLE terminal particles) maintained activity in the co-culture, while untargeted therapies (soluble scIL-12) showed much larger reduction in activity in co-culture. (*** indicates p<0.001 using one-way ANOVA with Bonferroni post test).

FIG. 2E shows fold change of MC38 co-culture experiment EC50 (FIG. 2D) over that of the splenocyte only culture (FIG. 2C).

FIG. 3 is a plot of starting weight (%) versus time, which is used as a measure of particle toxicity. Mice were treated with 5 µg/mouse/day over 5 days of PLE terminal layer Ni-HIS associated scIL-12 particles (n=5) monitoring their weight daily at the time of injection. This treatment was compared to PBS injections of equal volume, particles without scIL-12 at equivalent dosing, soluble scIL-12 at equivalent dosing, and 1.5x dosing of particle bound scIL-12 (all n=3). Both particle doses showed significantly lower toxicity than the soluble cytokine, which reached 10% weight loss by day 5. Samples were compared using two-way ANOVA with Bonferroni post test.

FIG. 4 is a schematic representation of layer-by-layer coating of particles.

FIG. 5A is a plot showing the efficiency with which particles coated with dextran sulfate target immune cells. Fluorescent core particles were coated with PLR followed by DXS and incubated in whole splenocyte culture for 18 hrs. Cultures were then measured for particle associated fluorescence by flow cytometry. Immune populations were gated by non-immune cells: CD45-, Dendritic Cells CD45+ CDllc+, Leukocytes CD45+ CDllb+, T cells: CD45+ CD3+, B cells CD45+ B220+. Data show histograms of cell number on the y-axis with median fluorescence intensity in the particle channel in the x-axis.

FIG. 5B is a plot showing the efficiency with which particles coated with hyaluronic acid target immune cells (similar to FIG. 5A).

FIG. 5C is a plot showing the efficiency with which particles coated with poly(L-glutamic acid) target immune cells (similar to FIG. 5A).

FIG. 5D is a plot showing the efficiency with which control particles target immune cells (similar to FIG. 5A).

FIG. 5E is a plot showing the efficiency with which uncoated particles target immune cells (similar to FIG. 5A).

FIG. 6A is a bar graph showing serum cytokine responses (pg/mL) after various treatments. Serum was collected 3 hours after the final dose from FIG. 3 .

FIG. 6B is a bar graph showing serum cytokine responses (pg/mL) after various treatments. Serum was collected 3 hours after the final dose from FIG. 3 .

FIG. 7 is a graph showing temporal response of IFN-γ, delivered exogenous HIS-tagged scIL-12, and endogenously produced IL-12 in MC38 tumors after intratumoral treatment with 5 µg Ni-HIS particles with PLE terminal layer.

FIGS. s 8A-8H show efficacy of the PLE terminal Ni conjugated scIL-12 nanoparticles treatment on the MC38 mice tumors. The data show individual mice tumor volumes by treatment, comparison of average tumor volumes on Day 13, and survival across treatment groups.

FIG. 8A MC38 tumor volumes of individual mice treated intratumorally with PBS weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8B MC38 tumor volumes of individual mice treated intratumorally with control nanoparticles (no scIL-12 loading, PLE terminal particles) weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8C MC38 tumor volumes of individual mice treated intratumorally with 5 µg scIL-12 loaded Ni-HIS particles with PLE terminal layer weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8D MC38 tumor volumes of individual mice treated intratumorally with 5 µg soluble scIL-12 weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8E MC38 tumor volumes of individual mice treated intratumorally with 7.5 µg scIL-12 loaded Ni-HIS particles with PLE terminal layer weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8F MC38 tumor volumes of individual mice treated intratumorally with 5 µg scIL-12 loaded Ni-HIS particles with PLE terminal layer 2x weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 8G Average tumor volumes on day 13 from FIGS. 8A-8F. Significance measured by one-way ANOVA with Bonferonni posttest. *** corresponds to p<0.001.

FIG. 8H Survival data of FIGS. 8A-8F. Significance measured by Log-rank tests.

FIGS. 9A-9I show MC38 tumors abscopal response to the treatment with PLE terminal Ni conjugated scIL-12 nanoparticles. Data show tumor volume of both treated and contralateral tumors, average tumor sizes on day 17, and survival.

FIG. 9A MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with PBS weekly beginning day 6 after tumor inoculation for 5 treatments, treated tumors.

FIG. 9B MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with 5 µg soluble scIL-12 weekly beginning day 6 after tumor inoculation for 5 treatments, treated tumors.

FIG. 9C MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with 5 µg scIL-12 Ni-HIS particles with PLE terminal layer weekly beginning day 6 after tumor inoculation for 5 treatments, treated tumors.

FIG. 9D MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with PBS weekly beginning day 6 after tumor inoculation for 5 treatments, untreated tumors.

FIG. 9E MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with 5 µg soluble scIL-12 weekly beginning day 6 after tumor inoculation for 5 treatments, untreated tumors.

FIG. 9F MC38 tumor volumes of individual mice bearing 2 tumors, with one tumor treated intratumorally with 5 µg scIL-12 Ni-HIS particles with PLE terminal layer weekly beginning day 6 after tumor inoculation for 5 treatments, untreated tumors.

FIG. 9G Average tumor sizes on day 17 from FIGS. 9A-9C.

FIG. 9H Average tumor sizes on day 17 from FIGS. 9D-9F.

FIG. 9I Survival from FIGS. 9A-9F.

FIGS. 10A-10F shows efficacy of the PLE terminal Ni conjugated scIL-12 nanoparticles treatment on the HM-1 mice tumors. Data show individual mice tumor volumes by treatment, comparison of average tumor volumes on Day 27, and survival across treatment groups.

FIG. 10A HM-1 tumor volumes of individual mice treated intratumorally with PBS weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 10B HM-1 tumor volumes of individual mice treated intratumorally with control nanoparticles (no scIL-12 loading, PLE terminal particles) weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 10C HM-1 tumor volumes of individual mice treated intratumorally with 5 µg scIL-12 loaded Ni-HIS particles with PLE terminal layer weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 10D HM-1 tumor volumes of individual mice treated intratumorally with 5 µg soluble scIL-12 weekly beginning day 6 after tumor inoculation for 5 treatments.

FIG. 10E Average tumor volumes on day 24 from FIGS. 10A-10D. Significance measured by one-way ANOVA with Bonferonni post test. ** corresponds to p<0.01.

FIG. 10F Survival data of FIGS. 10A-10D. Significance measured by Log-rank tests.

DETAILED DESCRIPTION OF THE INVENTION Overview

In certain embodiments, the invention relates to developing delivery systems for proteins, such as cytokines, that exhibit improved safety profiles. For example, in certain embodiments, the invention relates to a single-chain version of IL-12 (scIL-12) in a layer-by-layer nanoparticle that packages the cytokine in a manner that avoids off-target toxicity while maintaining its bioactivity.

Loading proteins, such as IL-12 and similar cytokines, into particles can be a challenge because proteins are very susceptible to conformational changes brought about by heat, sonication, or pH changes, all of which are common in formulating particles for delivering active agents.

To maintain its therapeutic efficacy, the protein must be encapsulated in such a way that it is able to interact with an external receptor found on T and natural killer (NK) cells. This poses a challenge because particles are usually designed to be internalized, and these immune cells are relatively rare in the tumor environment. Therefore, in addition to designing the particles for drug release, in certain embodiments, the particles comprise different polymeric coating materials for targeting the particle to the tumor as a method of avoiding off target exposure.

In certain embodiments, layer-by-layer technology is used to tailor the delivery properties of the particle in order to maximize the efficacy of anticancer agent in the tumor while keeping its off-target toxicity in check. Layer-by-layer nanoparticles may be created by using electrostatic and metallic affinity interactions to coat a colloidal substrate with polymeric materials. The addition of layered materials allows for optimized targeting and delivery of the payload as well as the combination of different payloads within a single particle.

In certain embodiments, the invention relates to particles where the protein is effectively encapsulated. In certain embodiments, the invention relates to particles that exhibit activity on external receptors in a relatively rare cell population in a tumor. In certain embodiments, the invention relates to particles exhibiting reduced toxicity while maintaining efficacy against a tumor challenge.

Glossary

As used herein, the term “monomer,” unless otherwise indicated, includes both isolated monomers and residues of monomers in an oligomer or a polymer (i.e. repeat units or residues).

The term “polyelectrolyte”, as used herein, refers to a polymer which under a particular set of conditions (e.g., physiological conditions) has a net positive or negative charge. In some embodiments, a polyelectrolyte is or comprises a polycation; in some embodiments, a polyelectrolyte is or comprises a polyanion. Polycations have a net positive charge and polyanions have a net negative charge. The net charge of a given polyelectrolyte may depend on the surrounding chemical conditions, e.g., on the pH. Exemplary polyelectrolytes for use in polymeric coatings in the compositions of the invention include, but are not limited to: poly(L-arginine) (PLR), poly-L-glutamic acid (PLE), polyarginine, polyglutamic acid, polylysine, heparin folate, heparin sulfate, fucoidan, sulfated-β-cyclodextrin, hyaluronic acid (HA), polyglutamic acid-block-polyethylene glycol, polyaspartic acid, polystyrene sulfonate (SPS), polyacrylic acid (PAA), linear poly(ethylene imine) (LPEI), poly(diallyldimethyl ammonium chloride) (PDAC), polyallylamine hydrochloride (PAH), poly(L-lactide-co-L-lysine), polyserine ester, poly(4-hydroxy-L-proline ester), poly[α-(4-aminobutyl)-L-glycolic acid], sodium polystyrene sulfonate, dextran sulfate (DXS), alginate, and chondroitin sulfate.

In certain embodiments, linkers (also known as “linker molecules” or “crosslinkers” or “spacers”) may be used to conjugate one atom to another in a composition. The majority of known linkers react with amine, carboxyl, and sulfhydryl groups. Linker molecules may be responsible for different properties of the composition. The length of the linker should be considered in light of molecular flexibility during the conjugation step, and the availability of the conjugated molecule for its target. Longer linkers may thus improve the biological activity of the compositions of the invention, as well as the ease of preparation of them. The geometry of the linker may be used to orient a molecule for optimal reaction with a target. A linker with flexible geometry may allow the entire composition to conformationally adapt as it binds a target sequence. The nature of the linker may be altered for other various purposes. For example, the hydrophobicity of a polymeric linker may be controlled by the order of monomeric units along the polymer, e.g. a block polymer in which there is a block of hydrophobic monomers interspersed with a block of hydrophilic monomers.

The chemistry of preparing and utilizing a wide variety of molecular linkers is well-known in the art and many pre-made linkers for use in conjugating molecules are commercially available from vendors such as Pierce Chemical Co., Roche Molecular Biochemicals, United States Biological. Exemplary linker molecules for use in the compositions of the invention include, but are not limited to: aminocaproic acid (ACA); polyglycine, and any other amino acid polymer, polymers such as polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polypropylene glycol (PPG); homobifunctional reagents such as APG, AEDP, BASED, BMB, BMDB, BMH, BMOE, BM[PEO]3, BM[PEO]4, BS3, BSOCOES, DFDNB, DMA, DMP, DMS, DPDPB, DSG, DSP (Lomant’s Reagent), DSS, DST, DTBP, DTME, DTSSP, EGS, HBVS, Sulfo-BSOCOES, Sulfo-DST, Sulfo-EGS; heterobifunctional reagents such as ABH, AEDP, AMAS, ANB-NOS, APDP, ASBA, BMPA, BMPH, BMPS, EDC, EMCA, EMCH, EMCS, KMUA, KMUH, GMBS, LC-SMCC, LC-SPDP, MBS, MBuS, M2C2H, MPBH, MSA, NHS-ASA, PDPH, PMPI, SADP, SAED. SAND, SANPAH, SASD, SATP, SBAP, SFAD, SIA, SIAB, SMCC, SMPB, SMPH, SMPT, SPDP, Sulfo-EMCS, Sulfo-GMBS, Sulfo-HSAB, Sulfo-KMUS, Sulfo-LC-SPDP, Sulfo-MBS. Sulfo-NHS-LC-ASA, Sulfo-SADP, Sulfo-SANPAH, Sulfo-SIAB, Sulfo-SMCC, Sulfo-SMPB, Sulfo-LC-SMPT, SVSB, TFCS; and trifunctional linkers such as Sulfo-SBED.

Branched linkers may be prepared or used so that multiple moieties per linker are able to react. Such multiply reactive linkers allow the creation of multimeric binding sites.

The term “pKa,” as used herein, includes the negative decadic logarithm of the ionization constant (Ka) of an acid; equal to the pH value at which equal concentrations of the acid and conjugate base forms of a substance (often a buffer) are present.

The term “hydrophobic,” as used herein, refers to a compound that has an octanol/water partition coefficient (Kow) greater than about 10 at about 23 oC.

The term “hydrophilic,” as used herein, refers to a compound that has an octanol/water partition coefficient (Kow) less than about 10 at about 23 oC.

As used herein, the term “pharmaceutically acceptable carrier” refers to a pharmaceutically-acceptable material, composition or vehicle for administration of an active agent described herein. Pharmaceutically acceptable carriers include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like which are compatible with the activity of the active agent and are physiologically acceptable to the subject. Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (i) sugars, such as lactose, glucose and sucrose; (ii) starches, such as com starch and potato starch; (iii) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, methylcellulose, ethyl cellulose, microcrystalline cellulose and cellulose acetate; (iv) powdered tragacanth; (v) malt; (vi) gelatin; (vii) lubricating agents, such as magnesium stearate, sodium lauryl sulfate and talc; (viii) excipients, such as cocoa butter and suppository waxes; (ix) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, com oil and soybean oil; (x) glycols, such as propylene glycol; (xi) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol (PEG); (xii) esters, such as ethyl oleate and ethyl laurate; (xiii) agar; (xiv) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (xv) alginic acid; (xvi) pyrogen-free water; (xvii) isotonic saline; (xviii) Ringer’s solution; (xix) ethyl alcohol; (xx) pH buffered solutions; (xxi) polyesters, polycarbonates and/or polyanhydrides; (xxii) bulking agents, such as polypeptides and amino acids (xxiii) serum component, such as serum albumin, HDL and LDL; (xxiv) C2-C12 alcohols, such as ethanol; and (xxv) other non-toxic compatible substances employed in pharmaceutical formulations. Wetting agents, coloring agents, release agents, coating agents, sweetening agents, flavoring agents, perfuming agents, preservative and antioxidants can also be present in the formulation. For formulations described herein to be administered orally, pharmaceutically acceptable carriers include, but are not limited to pharmaceutically acceptable excipients such as inert diluents, disintegrating agents, binding agents, lubricating agents, sweetening agents, flavoring agents, coloring agents and preservatives. Suitable inert diluents include sodium and calcium carbonate, sodium and calcium phosphate, and lactose, while com starch and alginic acid are suitable disintegrating agents. Binding agents may include starch and gelatin, while the lubricating agent, if present, will generally be magnesium stearate, stearic acid or talc. If desired, the tablets may be coated with a material such as glyceryl monostearate or glyceryl distearate, to delay absorption in the gastrointestinal tract.

Pharmaceutically acceptable carriers can vary in a formulation described herein, depending on the administration route. The formulations described herein can be delivered via any administration mode known to a skilled practitioner. For example, the formulations described herein can be delivered in a systemic manner, via administration routes such as, but not limited to, oral, and parenteral, including intravenous, intramuscular, intraperitoneal, intradermal, and subcutaneous. In some embodiments, the formulations described herein are in a form that is suitable for injection. In other embodiments, the formulations described herein are formulated for oral administration.

When administering parenterally, a formulation described herein can be generally formulated in a unit dosage injectable form (solution, suspension, emulsion). The formulations suitable for injection include sterile aqueous solutions or dispersions. The carrier can be a solvent or dispersing medium containing, for example, water, cell culture medium, buffers (e.g., phosphate buffered saline), polyol (for example, glycerol, propylene glycol, liquid polyethylene glycol, and the like), suitable mixtures thereof. In some embodiments, the pharmaceutical carrier can be a buffered solution (e.g., PBS). Where necessary, the composition may also include a solubilizing agent and a local anesthetic such as lignocaine to ease pain at the site of the injection.

The formulations can also contain auxiliary substances such as wetting or emulsifying agents, pH buffering agents, gelling or viscosity enhancing additives, preservatives, colors, and the like, depending upon the route of administration and the preparation desired. Standard texts, such as “REMINGTON’S PHARMACEUTICAL SCIENCE”, 17th edition, 1985, incorporated herein by reference, may be consulted to prepare suitable preparations, without undue experimentation. With respect to formulations described herein, however, any vehicle, diluent, or additive used should have to be biocompatible with the active agents described herein. Those skilled in the art will recognize that the components of the formulations should be selected to be biocompatible with respect to the active agent. This will present no problem to those skilled in chemical and pharmaceutical principles, or problems can be readily avoided by reference to standard texts or by simple experiments (not involving undue experimentation).

For in vivo administration, the formulations described herein can be administered with a delivery device, e.g., a syringe. Accordingly, an additional aspect described herein provides for delivery devices comprising at least one chamber with an outlet, wherein the at least one chamber comprises a pre-determined amount of any formulation described herein and the outlet provides an exit for the formulation enclosed inside the chamber. In some embodiments, a delivery device described herein can further comprise an actuator to control release of the formulation through the outlet. Such delivery device can be any device to facilitate the administration of any formulation described herein to a subject, e.g., a syringe, a dry powder injector, a nasal spray, a nebulizer, or an implant such as a microchip, e.g., for sustained-release or controlled release of any formulation described herein.

The nomenclature used to define the peptides is that typically used in the art wherein the amino group at the N-terminus appears to the left and the carboxyl group at the C-terminus appears to the right.

As used herein, the term “amino acid” includes both a naturally occurring amino acid and a non-natural amino acid. The term “amino acid,” unless otherwise indicated, includes both isolated amino acid molecules (i.e. molecules that include both, an amino-attached hydrogen and a carbonyl carbon-attached hydroxyl) and residues of amino acids (i.e. molecules in which either one or both an amino-attached hydrogen or a carbonyl carbon-attached hydroxyl are removed). The amino group can be alpha-amino group, beta-amino group, etc. For example, the term “amino acid alanine” can refer either to an isolated alanine H-Ala-OH or to any one of the alanine residues H-Ala-, -Ala-OH, or -Ala-. Unless otherwise indicated, all amino acids found in the compounds described herein can be either in D or L configuration. The term “amino acid” includes salts thereof, including pharmaceutically acceptable salts. Any amino acid can be protected or unprotected. Protecting groups can be attached to an amino group (for example alpha-amino group), the backbone carboxyl group, or any functionality of the side chain. As an example, phenylalanine protected by a benzyloxycarbonyl group (Z) on the alpha-amino group would be represented as Z-Phe-OH.

A protected amino acid is an amino acid in which one or more functional groups are protected with a protecting group. A protected peptide fragment is a dipeptide, tripeptide, or tetrapeptide, in which one or more functional groups of the amino acid of the peptide fragment are protected with a protecting group. Preferably, the protected amino acid and/or protected peptide fragment of the present invention have a protected amino group. The term “amino protecting group” refers to protecting groups which can be used to replace an acidic proton of an amino group in order to reduce its nucleophilicity.

Examples of amino protecting groups (e.g. X1, X2, X3, X4, etc.) include but are not limited to substituted or unsubstituted groups of acyl type, such as the formyl, acrylyl (Acr), benzoyl (Bz), acetyl (Ac), trifluoroacetyl, substituted or unsubstituted groups of aralkyloxycarbonyl type, such as the benzyloxycarbonyl (Z), p-chlorobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, benzhydryloxycarbonyl, 2(p- biphenylyl)isopropyloxycarbonyl, 2-(3,5-dimethoxyphenyl)isopropyloxycarbonyl, p-phenylazobenzyloxycarbonyl, triphenylphosphonoethyloxycarbonyl or 9-fluorenylmethyloxycarbonyl group (Fmoc), substituted or unsubstituted groups of alkyloxycarbonyl type, such as the tert-butyloxycarbonyl (BOC), tert-amyloxycarbonyl, diisopropylmethyloxycarbonyl, isopropyloxycarbonyl, ethyloxycarbonyl, allyloxycarbonyl, 2 methylsulphonylethyloxycarbonyl or 2,2,2-trichloroethyloxycarbonyl group, groups of cycloalkyloxycarbonyl type, such as the cyclopentyloxycarbonyl, cyclohexyloxycarbonyl, adamantyloxycarbonyl or isobornyloxycarbonyl group, and groups containing a hetero atom, such as the benzenesulphonyl, p-toluenesulphonyl, mesitylenesulphonyl, methoxytrimethylphenylsulphonyl, 2-nitrobenzenesulfonyl, 2-nitrobenzenesulfenyl, 4- nitrobenzenesulfonyl or 4-nitrobenzenesulfenyl group. Among these groups X, those comprising a carbonyl, a sulfenyl or a sulphonyl group are preferred. An amino protecting groups X1, X2, X3, X4, etc. is preferably selected from allyloxycarbonyl groups, tert-butyloxycarbonyl (BOC), benzyloxycarbonyl (Z), 9 fluorenylmethyloxycarbonyl (Fmoc), 4-nitrobenzenesulfonyl (Nosyl), 2-nitrobenzenesulfenyl (Nps) and substituted derivatives.

Preferred amino protecting groups X1, X2, X3, X4, etc. for the process of the present invention are tert-butyloxycarbonyl (Boc), a 9-fluorenylmethyloxycarbonyl (Fmoc), and a benzyloxy-carbonyl (Z). Even more preferred amino protecting groups for the process of the present invention are tert-butyloxycarbonyl (Boc) and a benzyloxy-carbonyl (Z).

Amino protecting groups X1, X2, X3, X4, etc. can be introduced by various methods as known in the art. For example, by reaction with suitable acid halides or acid anhydrides. On the other hand, amino protecting groups X1, X2, X3, X4, etc. can be removed (i.e., the step of deprotecting), for example, by acidolysis, hydrogenolysis (e.g., in the presence of hydrogen (e.g. bubbled through the liquid reaction medium) and catalyst such as palladium catalyst), treatment with dilute ammonium hydroxide, treatment with hydrazine, treatment with sodium and treatment with sodium amide.

As used herein, the term “tag” refers to a compound, for example a peptide, that can be used for purification, for solubilization, chromatography, as epitope tags, fluorescence tags, and others. Tags useful in the present invention include, but are not limited to, BCCP, c-myc-tag, Calmodulin-tag, FLAG-tag, HA-tag, His-tag, Maltose binding protein-tag, Nus-tag, Glutathione-S-transferase (GST) tag, Green fluorescent protein-tag, Thioredoxin-tag, S-tag, Streptag II, Softag 1, Softag 3, T7-tag, Elastin-like peptides, Chitin-binding domain, and Xylanase 10A.

As used herein, the term “affinity” refers to the equilibrium constant for the reversible binding of two agents (e.g., tag and a ligand, or a metal ion and a ligand) and is expressed as a dissociation constant (KD). Affinity can be at least 1-fold greater, at least 2-fold greater, at least 3-fold greater, at least 4-fold greater, at least 5-fold greater, at least 6-fold greater, at least 7-fold greater, at least 8-fold greater, at least 9-fold greater, at least 10-fold greater, at least 20-fold greater, at least 30-fold greater, at least 40-fold greater, at least 50-fold greater, at least 60-fold greater, at least 70-fold greater, at least 80-fold greater, at least 90-fold greater, at least 100-fold greater, or at least 1,000-fold greater, or more, than the affinity of a ligand for unrelated peptides or compounds. Affinity of a ligand to its binding partner can be, for example, from about 100 nanomolar (nM) to about 0.1 nM, from about 100 nM to about 1 picomolar (pM), or from about 100 nM to about 1 femtomolar (fM) or more. An “affinity ligand” is a ligand having affinity for a binding partner.

As used herein, the term “associated with” refers to a direct association between two molecules, due to, for example, covalent, electrostatic, hydrophobic, and ionic and/or hydrogen-bond interactions.

As used herein, the term “coordinated with” refers to, in coordination chemistry, the association between a metal atom or metal ion and an ion or molecule (e.g., a functional group on a ligand). The binding between metal and ligand generally involves formal donation of one or more of the ligand’s electron pairs. The nature of the metal-ligand bonding can range from covalent to ionic.

The terms “polypeptide,” “peptide,” and “protein”, used interchangeably herein, refer to a polymeric form of amino acids of any length, which can include genetically coded and non-genetically coded amino acids, chemically or biochemically modified or derivatized amino acids, and polypeptides having modified peptide backbones. The term includes fusion proteins, including, but not limited to, fusion proteins with a heterologous amino acid sequence, fusions with heterologous and homologous leader sequences, with or without N-terminal methionine residues; immunologically tagged proteins; and the like. An example of a protein is an antibody.

As used herein, the term “peptide fragment” refers to two or more amino acids covalently linked by at least one amide bond (i.e. a bond between an amino group of one amino acid and a carboxyl group of another amino acid selected from the amino acids of the peptide fragment). The terms “polypeptide” and “peptide fragments” are used interchangeably. The term “peptide fragment” includes salts thereof, including pharmaceutically acceptable salts.

A cytokine is a signaling protein regulating biological functions such as innate and acquired immunity, hematopoiesis, inflammation and repair, and proliferation through mostly extracellular signaling.

Interleukin 12 (Il-12 or IL-12) is a cytokine that is naturally produced by dendritic cells, macrophages, neutrophils, and human B-lymphoblastoid cells in response to antigenic stimulation. Il-12 is composed of a bundle of four alpha helices. It is a heterodimeric cytokine encoded by two separate genes, Il-12A (p35) and I1-12B (p40).

Single chain interleukin 12 (scIl-12) is a protein in which the p35 and p40 subunits of heterodimeric IL-12 are covalently bonded together. For example, interleukin 12 can be monomerized by introduction of a peptide linker between the p35 and p40 protein chains of the heterodimeric cytokine. scIL-12 may be a fusion protein.

In certain embodiments, the invention relates to a particle comprising a liposome. In certain embodiments the liposome comprises a first lipid covalently bonded to an affinity ligand. In certain embodiments the first lipid forms an outer surface of the liposome. In certain embodiments, the invention relates to a particle comprising a protein covalently bonded to a tag. In certain embodiments the tag is associated with the affinity ligand. In certain embodiments, the invention relates to a particle comprising a polymer coating. In certain embodiments, the invention relates to a particle comprising the polymer coating comprising at least one layer including a polycation. In certain embodiments the polycation is non-covalently associated with the outer surface of the liposome. In certain embodiments, the invention relates to a particle comprising at least one layer including a polyanion. In certain embodiments the polyanion is non-covalently associated with the at least one polycation layer.

In certain embodiments, the invention relates to a particle comprising a metal ion. In certain embodiments, the invention relates to a particle comprising an affinity ligand which is a metal-affinity ligand. In certain embodiments, the invention relates to a particle comprising a tag which is a peptide tag. In certain embodiments, the invention relates to a particle comprising a metal ion that is coordinated with the metal-affinity ligand, thereby forming a metal-coordinated ligand. In certain embodiments, the invention relates to a particle comprising the peptide tag which is associated with the metal-coordinated ligand.

In certain embodiments, the invention relates to a particle comprising the affinity ligand which is non-covalently associated with the tag.

In certain embodiments, the invention relates to a particle comprising the affinity ligand which is covalently associated with the tag.

In certain embodiments, the invention relates to a particle comprising the metal-coordinated ligand which is non-covalently associated with the peptide tag.

In certain embodiments, the invention relates to a particle comprising the metal-affinity ligand which is iminodiacetic acid or iminodipropionic acid.

In certain embodiments, the invention relates to a particle comprising the metal ion selected from the group consisting of Fe(III), Co(II), Ni(II), Cu(II), and Zn(II).

In certain embodiments, the invention relates to a particle comprising the metal ion that is Ni(II).

In certain embodiments, the invention relates to a particle comprising the peptide tag which is at least two amino acid monomers in length.

In certain embodiments, the invention relates to a particle comprising the peptide tag which is at least three amino acid monomers in length.

In certain embodiments, the invention relates to a particle comprising the peptide tag which comprises a histidine monomer.

In certain embodiments, the invention relates to a particle comprising the peptide tag which comprises at least two histidine monomers.

In certain embodiments, the invention relates to a particle comprising the peptide tag which is a His6 tag.

In certain embodiments, the invention relates to a particle comprising the peptide tag which is covalently bonded to the C-terminus of the protein.

In certain embodiments, the invention relates to a particle comprising the first lipid which is 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl].

In certain embodiments, the invention relates to a particle comprising a second lipid; and the second lipid is a phosphatidylcholine.

In certain embodiments, the invention relates to a particle comprising the second lipid which is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC).

In certain embodiments, the invention relates to a particle comprising a third lipid.

In certain embodiments, the invention relates to a particle comprising a third lipid which is 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG).

In certain embodiments, the invention relates to a particle comprising a fourth lipid; and the fourth lipid is cholesterol.

In certain embodiments, the invention relates to a particle comprising a protein which is non-covalently associated with the affinity ligand on the outer surface of the liposome.

In certain embodiments, the invention relates to a particle comprising a protein; and the protein is a cytokine.

In certain embodiments, the invention relates to a particle comprising a cytokine; and the cytokine is an interleukin or an interferon, or a single-chain variant of an interleukin or an interferon.

In certain embodiments, the invention relates to a particle comprising a cytokine; and the cytokine is an interleukin or a single-chain variant of an interleukin.

In certain embodiments, the invention relates to a particle comprising a cytokine; and the cytokine is IL-12 or a single-chain variant of IL-12.

In certain embodiments, the invention relates to a particle comprising a cytokine; and the cytokine is a single-chain variant of IL-12.

In certain embodiments, the invention relates to a particle comprising polycation selected from the group consisting of polyarginine and polylysine.

In certain embodiments, the invention relates to a particle comprising polycation; and the polycation is polyarginine.

In certain embodiments, the invention relates to a particle comprising polycation; and the polycation is poly-1-arginine.

In certain embodiments, the invention relates to a particle comprising polyanion selected from Heparin Folate, Heparin Sulfate, Dextran Sulfate, Fucoidan, Sulfated-B-cyclodextrin, Hyaluronic acid, Polyglutamic acid, Polyglutamic acid-block-polyethylene glycol, Polyaspartic acid, and Poly acrylic acid.

In certain embodiments, the invention relates to a particle comprising polyanion selected from polyglutamic acid and hyaluronic acid.

In certain embodiments, the invention relates to a particle comprising polyanion selected from poly-1-glutamic acid and hyaluronic acid.

In certain embodiments, the invention relates to a particle comprising a second polycation coating non-covalently associated with the outer surface of the polyanion coating; and a second polyanion coating non-covalently associated with the outer surface of the second polycation coating.

In certain embodiments, the invention relates to a pharmaceutical formulation comprising a plurality of particles and a pharmaceutically acceptable carrier.

In certain embodiments, the invention relates to a method of treating cancer comprising administering to a subject in need thereof a therapeutically effective amount of a particle.

In certain embodiments, the invention relates to a method of treating cancer, wherein the subject is human.

In certain embodiments, the invention relates to a method of treating cancer wherein the composition is administered intravenously.

EXEMPLIFICATION

The invention now being generally described, it will be more readily understood by reference to the following, which is included merely for purposes of illustration of certain aspects and embodiments of the present invention, and is not intended to limit the invention.

Example 1 - Formation of Coated Liposomes

A liposomal core nanoparticle with 5% DGS-NTA (Ni) (1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl] nickel salt) lipid by mole was reacted with an scIL-12 construct which contains a 6xHIS tag at the c-terminus. This resulted in layering of the scIL-12 around the preformed liposome by Ni-HIS interaction. The scIL-12 liposome (which bears a negative charge) was then coated with a bilayer of poly(L-arginine) (PLR) and a terminal layer of polyanion using electrostatic interactions. The process of layer-by-layer particle formation is outlined in FIG. 4 , and the resulting scIL-12-containing particles are depicted in FIG. 1A. The addition of these layers allowed for increased targeting of the particle to the tumor and reduction in systemic scIL-12 exposure. The optimization of this particle manufacturing procedure allowed for >90% encapsulation of protein with a final weight percentage of 17% scIL-12 in the particle, a large improvement over other techniques such as passive loading in the liposome or cytokine-heparin interaction in the layers FIG. 1B. The structure of layered liposomes was confirmed by CryoEM imaging of particle solutions, showing well-formed liposomes with polymer layers, of monodisperse size approximately 80-150 nm.

Example 2 - Polymer Coating

A library of different external layer materials was tested for their tumor targeting and immune cell targeting capabilities to make the most effective delivery vehicle for scIL-12. A series of charged polypeptides have been studied as the external layers of nanoparticles, and have been shown to undergo differing amounts of binding versus internalization with different cell types. Flow cytometry was used to asses binding of particles to different cell types. Briefly, fluorescent core particles were coated with PLR followed by different polyanion terminal layers and incubated with different cell lines both cancerous and noncancerous for 24 hours. Cultures were then measured for particle associated fluorescence by flow cytometry. Hyaluronic acid and PLE terminal layers showed increased association with cancer cells as compared to noncancerous cell lines as measured by mean fluorescence intensity. Particles were measured for their association with immune populations by incubation with whole splenocytes for 18 hours. Immune populations were gated by non-immune cells: CD45-, Dendritic Cells CD45+ CDllc+, Leukocytes CD45+ CDllb+, T cells: CD45+ CD3+, B cells CD45+ B220+. Data show histograms of cell number on the y-axis with median fluorescence intensity in the particle channel in the x-axis (FIGS. 5A-5E). The data presented in FIGS. 5A-5E suggest these differences are based on specific interactions with proteins and glycans on the surfaces of cells of interest. These studies showed that hyaluronic acid (HA) and poly(L-glutamic acid) (PLE) have the highest association with cancer cells and relevant immune cells. Particles were further tested for subcellular localization via fluorescent microscopy. Fluorescent core particles were incubated for 6 or 24 hours on MC38 cancer cells. Cells were stained using wheat germ agglutinin to show the cell membrane and Hoechst to show the nucleus. These studies showed that PLE coated particles maintained greater degrees of extracellular, membrane bound association, while HA coated particles showed greater degrees of internalization.

Particles were formulated with both HA and PLE as the terminal layer, using either Ni-HIS loading or Heparin associated loading as described. These particles were tested in vitro for their ability to produce IFN-γ (a functional assay for IL-12 bioactivity) when incubated with primary murine splenocytes (FIGS. 2A, 2C). Splenocytes isolated from C57BL/6 mice were treated for 18 h with various formulations of scIL-12. Supernatants were measured with ELISA for IFN-γ production. Calculated EC50 values from nonlinear least squares fit with automatic outlier elimination in Prism 5 on log transformed, normalized data. Statistical significance calculated using 1-way ANOVA with Bonferroni post test (*** p<0.001). The IFN-γ responses and EC50 are shown in FIGS. 2A and 2C.

An additional in vivo mimic model was used, in which the particles are delivered to cancer cells, washed with PBS, and then primary murine splenocytes added to the treated cancer cells to ensure the particles maintained activity even after interaction with tumor cells which are much more prominent in the tumor microenvironment compared to target immune populations.

Sub-confluent tumor cells were treated with scIL-12 particles or control for 6 hours. Plates were washed with PBS and splenocyte cultures were added to wells for 18 hours. Supernatants were measured with ELISA for IFN-γ production. MC38 model statistical significance calculated using 1-way ANOVA with Bonferroni post test (*** p<0.001). The IFN-γ responses and EC50 are shown in FIGS. 2B and 2D.

As an additional measure of particle benefit over soluble therapy, the results shown in FIGS. 2C and 2D were combined as a measure of the maintenance of scIL-12 activity in the tumor environment. These results are shown in FIG. 2E as the fold change of MC38 co-culture EC50/Splenocyte only EC50.

These assays show that the nanoparticle formulations, particularly the Ni-HIS nanoparticles with PLE terminal layer, show enhanced activity over soluble scIL-12, with the PLE terminal layer performing best, particular in the tumor mimic co-culture environment and maintenance of activity.

Example 3 - Toxicity

A toxicity study was performed, delivering either 5 or 7.5 µg/mouse/day of scIL-12 in the Ni-HIS particles with PLE terminal layer over 5 days. Controls included 5 µg/mouse/day of soluble scIL-12 over the same period, particles without cytokine at equivalent dosing, and PBS. The mice were tracked for weight loss over the 5-day study period. The particle bound IL-12 showed a significant reduction in toxicity, losing negligible weight even at higher dosing compared to soluble IL-12 which saw approximately 10% reduction in body weight over 5 days FIG. 3 .

At the end of the 5-day period serum was collected from the different groups and measured for inflammatory cytokine levels. Cytokine storm (as evidenced by elevated levels of inflammatory cytokines in circulation) is the route by which IL-12 therapy shows toxicity. FIGS. 6A and 6B show serum cytokine response depending on the scIL-12 formulation. These data agree with the weight changes, showing that particle bound scIL-12, even at higher dosing levels, is less toxic than its soluble counterpart.

Example 4 - Tumor Challenge

Particle formulations were tested against a tumor challenge. MC38 and HM1 tumors grown subcutaneously were used.

MC38 temporal cytokine response: MC38 tumors were treated intratumorally with scIL-12 in PLE terminal Ni conjugated particles after tumors were allowed to establish for 7 days. Tumors were extracted at different time points, homogenized, and analyzed via ELISA for a cytokine response. The resulting data are presented in FIG. 7 . These data show that scIL-12 in Ni-HIS particles with PLE terminal layer are able to incite an immune response in the tumor lasting approximately 5-7 days.

MC38 In Vivo Efficacy: MC38 tumors were established on the right flank of C57B⅙ mice and allowed to grow for 6 days. On day 6 treatments were begun intratumorally. Mice were treated weekly with PBS, weekly with control particles (no IL-12), weekly with PLE terminal Ni conjugated scIL-12 at 5 µg dose, weekly with 5 µg soluble scIL-12, weekly with 7.5 µg scIL-12 in particles, or twice weekly with 5 µg scIL-12 in particles. All treatments were given for 5 doses. Data presented in FIGS. 8A-8F show individual mice tumor volumes by treatment, FIG. 8G shows comparison of average tumor volumes on Day 13, and FIG. 8H shows survival across treatment groups. Particle bound scIL-12 performs as well as soluble with the potential for improvement at increased frequency or amount of dosing.

MC38 Abscopal Response: Tumors were established on both left and right flank of C57B⅙ mice. Right flank tumors were treated day 6 after inoculation with PBS, 5 µg scIL-12 in particles or 5 µg scIL-12 soluble on a weekly basis for 5 doses. Data presented in FIGS. 9A-9F show tumor volume of both treated and contralateral tumors, FIGS. 9G-9H shows average tumor sizes on day 17, and FIG. 9I shows survival. Particles perform similar to soluble cytokine in the treated tumor, but slightly worse in contralateral tumors likely due to systemic leakage of the free cytokine, as exemplified in the toxicity data.

HM-1 In Vivo Efficacy: HM-1 tumors were established on the right flank of B6C3F1 mice (pairings of C57BL/6x C3H/HeN) and allowed to grow for 6 days. On day 6 treatments were begun intratumorally. Mice were treated weekly with PBS, weekly with control particles (no IL-12), weekly with PLE terminal Ni conjugated scIL-12 at 5 µg dose, weekly with 5 µg soluble scIL-12. Data presented in FIGS. 10A-10D show individual mice tumor volumes by treatment, FIG. 10E shows comparison of average tumor volumes on Day 24, and FIG. 10F shows survival across treatment groups. Particle bound scIL-12 performs as well as soluble with the potential for improvement at increased frequency or amount of dosing.

Particle immune activity will be tested by testing efficacy of treatment on contralateral tumors and rechallenging subjects that respond to treatment with additional tumor cells.

Example 5 - Treatment Scheduling

Various treatment schedules will be examined. Specific tumor targeting and biodistribution will be tested as a function of dosing schedule.

Example 6 - Combination Therapies

Combination therapy particles will be formulated by including additional drugs (chemotherapy, synergistic cytokines, etc.) in unused particle compartments (liposome core, layers).

INCORPORATION BY REFERENCE

The contents of the articles, patents, and patent applications, and all other documents and electronically available information mentioned or cited herein, are hereby incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. Applicant reserves the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other physical and electronic documents.

EQUIVALENTS

The inventions have been described broadly and generically herein. Those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The inventions are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of embodiments of the invention. Further, each of the narrower species and subgeneric groupings falling within the generic disclosure also form parts of the inventions. This includes the generic description of embodiments of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein. 

1-20. (canceled)
 21. A particle comprising: a liposome, wherein the liposome comprises a first lipid covalently bonded to an affinity ligand; and the first lipid forms an outer surface of the liposome; a cytokine covalently bonded to a tag, wherein the tag is associated with the affinity ligand, and wherein the cytokine binds a receptor on the surface of an immune cell when the particle contacts a cancer cell; and a polymer coating, wherein the polymer coating comprises: at least one layer including a polycation, wherein the polycation is non-covalently associated with the outer surface of the liposome; and at least one layer including polyglutamic acid, wherein the polyglutamic acid is non-covalently associated with the at least one polycation layer.
 22. The particle of claim 21, further comprising a metal ion, wherein: the affinity ligand is a metal-affinity ligand; the tag is a peptide tag; the metal ion is coordinated with the metal-affinity ligand, thereby forming a metal-coordinated ligand; the peptide tag is associated with the metal-coordinated ligand.
 23. The particle of claim 22, wherein the metal-coordinated ligand is non-covalently associated with the peptide tag.
 24. The particle of claim 23, wherein the metal-affinity ligand is iminodiacetic acid or iminodipropionic acid.
 25. The particle of claim 23, wherein the metal ion is selected from the group consisting of Fe(III), Co(II), Ni(II), Cu(II), and Zn(II).
 26. The particle of claim 23, wherein the peptide tag is at least two amino acid monomers in length.
 27. The particle of claim 23, wherein the peptide tag comprises a histidine monomer.
 28. The particle of claim 21, wherein the first lipid is 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl].
 29. The particle of claim 21, wherein the liposome further comprises a second lipid; and the second lipid is a phosphatidylcholine.
 30. The particle of claim 21, wherein the liposome further comprises a third lipid.
 31. The particle of claim 21, wherein the liposome further comprises a fourth lipid; and the fourth lipid is cholesterol.
 32. The particle of claim 21, wherein the tag is non-covalently associated with the affinity ligand on the outer surface of the liposome.
 33. The particle of claim 21, wherein the tag is covalently associated with the affinity ligand on the outer surface of the liposome.
 34. The particle of claim 21, wherein the cytokine is a single-chain variant of IL-12.
 35. The particle of claim 21, wherein the polycation is selected from the group consisting of polyarginine and polylysine.
 36. The particle of claim 21, wherein the particle further comprises a second polycation coating non-covalently associated with the outer surface of the polyglutamic acid coating; and a second polyglutamic acid coating non-covalently associated with the outer surface of the second polycation coating.
 37. The particle of claim 21, wherein the first lipid covalently bonded to the affinity ligand is 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl]; the particle further comprises a metal ion selected from the group consisting of Fe(III), Co(II), Ni(II), Cu(II), and Zn(II); the metal ion is coordinated with the affinity ligand, thereby forming a metal-coordinated ligand; the metal-coordinated ligand is non-covalently associated with the tag; the tag is a peptide tag; the peptide tag is at least two amino acid monomers in length; the peptide tag comprises a histidine monomer; the cytokine is a single-chain variant of IL-12; and the polycation is selected from the group consisting of polyarginine and polylysine.
 38. The particle of claim 21, wherein the at least one layer including polyglutamic acid has an affinity for the cancer cell.
 39. A pharmaceutical formulation comprising a plurality of particles of claim 21, and a pharmaceutically acceptable carrier.
 40. A method of treating cancer comprising administering to a subject in need thereof a therapeutically effective amount of a particle of claim
 21. 41. The method of claim 40, wherein the cancer is colon cancer or ovarian cancer. 